Back-digger boom construction



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Zei/man,

Phl INVENTOR. er' OMPM HSATTRNEYS.

Patented June 22, 1937 BACK-BIGGER BOOM CONSTRUCTION Roy H. Zeilman,Lorain, Ohio, alsignor'to Thew Shovel Company, Lorain, Ohio, acorporation of Ohio Application July 11, 1936, Serial No. 90,238

4 Claims.

This in'ventlon relates to boom constructions, and more particularly toan improved boom construction adapted to power operated excavatingmachines of the back-digger type.

The back-digger type of excavating machines usually comprises a dipperstick supported at the boom outer end and movement ef the boom anddipper stick is controlled by cables secured to the dipper and the upperend of the dipper stick. Due to the dipper stick being supported at theouter end of the boom and extended therebeyond during diggingoperations, the boom'is subjected to considerable stress particularly incompression and torsion. Also, since the cables leading to the dipperare reeved through sheaves disposed generally centrally of the boom, theboom is subjected to a considerable bending moment. The greatest stresswill occur in portions of the boom remote from the boom foot or theouter portion of the boom.

Heretofore, it has been customary to provide a relatively heavy boom tocare for these stresses and due to the difference in operatingconditionsand boom loading, booms adapted to other type excavatingmachines have not been adaptable to back-diggerrmachines.

I have provided a. boom construction for backdigger machines which isrelatively light and a 'detachable member transmits a large portion ofthe stresses encountered in the outer portion of the boom. Due to thedetachable arrangement of this member power shovel and the like boomsmay be easily converted to back-digger booms.

It is an object of my invention therefore to provide a boom structurefor excavating machines having a supplemental stress member in the outerpo rtion of the boom.

Another object of my invention is to provide a boom of the above typewhich is of improved construction relative to the transmission ofbending and torsional strains.

Another object of my invention is to provide a boom of the above typewhich may be relatively economically manufactured and assembled andwhich is of rugged construction compared to the boom weight.

Other objects of my invention and the invention itself will becomeincreasingly apparent from a consideration of the following descriptionand drawings wherein:

v Fig. 1 is an elevational view of a back-digger type of excavatingmachine embodying my invention;

Figs. 2 and 3 are enlarged plan and elevational views respectively ofthe boom of Fig. 1;

Fig. 4 is a view of the boom of Figs. 2 and 3 prior to insertion of thesheave shafts and supplemental stress member;

Fig. 5 is a sectional view taken along line 5-5 0f F18. 2; and.

Fig. 6 is a fragmentary sectional view taken along line 8--8 of Fig. 3.1

Referring now to the drawingsI I have illustrated in Fig. 1 anexcavating machine of the back-digger type comprising a truck generallyindicated at I0 upon which is rotatably mounted a superstructuregenerally indicated at II comprising the power unit and associatedmechanism for controlling operation of the boom and supported parts andalso movement of the truck..

The superstructure I I is mounted on a turntable indicated at I2 and theboom I3 is hinged at its foot in the usual manner to a forward portionof the turntable. Cables I5 are reeved through sheaves I6 rotatablysecured to a dipper stick I1 which pivotally engages boom I3 and jointlywith a drag cable I8 secured to a drag bucket IS at the lower end of thedipper stick controls movementof the boom. The cable I5 is also reevedvthrough sheaves 2l! supported on an A frame 2| comprising part of thesuperstructure mounted on the turntable. A dead end of the cable I5 issecured as indicated at 22 and the opposite end after passing over oneof sheaves 2li is wound upon a. rotatable hoist drum (not shown)operable in the usual manner.

The drag cable I8 has a dead end secured in the usual manner to the boomadjacent its foot and then passes over one of two transversely spacedsheaves 23 and is reeved 'through a sheave 24 secured to the drag bucketI9, then it is reversely passed over the second of the pair of sheaves23 and through a fairead arrangement to a rotatable drum. In thismanner, the boom may be raised or lowered together with the partssupported thereby including the dipper stick and drag bucket throughmanipulation of the cables I5 and I8 in a manner well understood. Theoperation of the parts thus far described is well understood and afurther description is not believed necessary. The boom I3 comprisesside plates 25-25 generally channel-shaped in transverse sectiontapering from a zone of maximum depth generally centrally of the boomtowards each end, the channel form preferably being effected byproviding longitudinally extending angles which may be riveted orotherwise integrally secured to the sideplate along the top and bottomedges and with the horizontally extending flanges of the angles inwardlydisposed. Transverse spacing plates reinforced by angles may be Providedat the lower end of the boom as indicated at 26 and adjacent the outerend of the boom as indicated at 21 which together with a topplate 28 anddiagonal tie members 29 comprise the 'transverse spacing members.Rearwardly extending arms at the boom foot indicated at 30 areperforated for the reception of hinge pins side-plates 25 with theprojecting U legs being provided with transversely aligned perforationsfor the reception vof a shaft 34.

As best illustrated-in Figs. 2 and 5, an element generally indicated ,at35 comprising a central generally box-shaped portion 36 and cylindricalend portions 31--31 is provided with a relatively large transverse borethrough the centralportion 36 for the reception of a tubular member 38,the tubular member 38 preferably prior to assembly v.with element 35being bored to co-axially align with the cylindrical end portions 31-31.The cylindrical end portions form bearings foi` the sheaves 23 which aretelescoped thereover and upon projecting the tubular element 38 axiallyfromv the outer end of the boom to the position illustrated in Fig. 2and weldingly securing the same to the member 35 along circular zonesindicated at 39 and 4U the shaft 32 may be projected through'element 35and bearing elements 3|. Suitable spacing washers 4I may be providedintermediate the bearing elements and the outer faces of the sheave hubportion.

The opposite end of tubular element 38 is integrally secured to anaxially extending tubular portion 42 of a transverselylextending plateelement 43 by telescoping portion 42 thereinto and weldingly unitingplate element 43 with the tubular element 38. The plate element 43 isperforated as indicated at 44fwhereby it may be secured to a stiffenerplate 45 by bolts 46 and4 nuts 41. The plate 2l is provided with aperforation 48 affording ample-clearance for tubular element 38.

The shaft 34 forms a mounting for guide sheaves for cable I5 and alsofor perforated and rearwardly extending arms 49 of a yoke element 50,the shaft being projected through the perforated arms of member 33 andsecured against transverse movement in any suitable manner as by theprovision of collars 5I. The yoke element 50 is integrally secured tothe dipper stick I'l whereby the dipper stick may cooperate with theboom I3 in a manner well understood to control movement of the dipperI9.

It will be observed that the elements 35 and 43 are each integrallyunited with the tubular element 38 whereby torsional stressesencountered when the side of the dipper I9 strikes an obstruction orwhen rapidly swinging the boom in a lateral direction are absorbedclosely adjacent the shaft 34 which transmits such torsional stress tothe plate element 43 by the U-member 33 and which stress, in turn, istransmitted to the shaft 32 by tubular element 38 and thence to the boomside plates at substantially the mid-portion of the boom; The stress isthen transmitted through the boom proper to the boom foot. -Thusl, theboom is largely relieved of torsional stresses in its weakest portion or'the portion outwardly from the mid-point of the boom. In a similarmanner, a large portion of the compression stresses are transmitted-bythe tubular element 33 and the boom side plates 25 are proportionatelyrelieved of compression stresses and primarily absorb thev bendingstresses. v

I have described the assembly of the supplemental stress member with theboom as adapting a boom structure illustrated in Fig. 4 to a back-diggerboom at the scene of operations or in the field but it is understoodthat the manner of assembly may be varied as desired or in -accordancewith best shop practice when assembled at the factory.

Although I have shown and described modifications of my invention Icontemplate that numerous and extensive departures may be made there- Yfrom withoutdeparting from the spirit of my invention and the scope ofthe appended claims.

Having thus described my invention what I claim is: 4

1. A boom construction adapted to back-digger type excavating machines,comprising spaced longitudinally extending side plates, transverselyaligned bearing elements inthe side plates generally centrally of theboom, a sheave supporting shaft rotatably mounted in the bearingelements, a transversely extending element rigidly fixed to the sideplates adjacent their outer ends, and a tubular element rigidly securedto the transverse element at one end of said tubular element and at-itsopposite end encircling the type excavating machines, comprisingtransversely spaced longitudinallyextending side plates, transverselyaligned bearing elements in the side plates generally centrally of theboom, a removable shaft rotatably mounted in the bearings, a transverseelement integrally secured to the side plates adjacent to the outeren`d, and a tubular element detachably secured to the transversevelement and encircling the shaft adapted to transmit torsional stressfrom the boom outer end to the boom central portion.

4. The method of converting a boom comprising transversely spacedlongitudinally extending side plates into a back-digger boom adapted towithstand severe torsional and compression stresses intermediate theboom outer end and central portions, the method including projecting atubular element into the boom axially thereof, transversely mounting ashaft having an encircling element associated therewith in the sideplates generally centrally of the boom, weldingly securing the inner endof the tubular element to Ithe encircling element, integrally securing atransverse element tothe side plates adjacent the boom outer end, anddetachably securing the outer end of the tubular element to thetransverse element. l

ROY H. ZEILMAN.

